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2017 the year of tennis comebacks

Federer returns from knee injury

Sharapova returns from drug ban

Nadal, Serena also return from injuries

(CNN)If 2016 was a season of memorable firsts in tennis, call 2017 the year of the comeback. Roger Federer, Maria Sharapova, Serena Williams and Nick Kyrgios -- and there are more -- are among those returning to the circuit after being sidelined for differing reasons.

Yet another player to make a comeback is Nick Kyrgios. The reason he was out? The Australian was banned for eight weeks by the ATP tour in October for, essentially, a lack of effort.

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In grand slams, he'll make his return in time for the Australian Open, Kyrgios' home major in Melbourne.

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Will Serena Williams surpass Steffi Graf and become the first player in the Open Era to win 23 majors?

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Williams -- yes -- is also coming back. The 35-year-old hasn't played since September because of a shoulder injury.

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Will Novak Djokovic rediscover his mojo? Djokovic was tennis' top player in the first half of 2016 but tailed off considerably.

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Djokovic and coach Boris Becker parted company in early December, with the Serb not yet naming a replacement.

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He was, don't forget, ranked third in July just before deciding to skip the rest of 2016 to rehabilitate his knee.

Federer was due to make a high-profile comeback earlier this month in the exhibition IPTL but didn't play due to, as the struggling Asian-based league put it, the "current economic climate in India and uncertainty of spending money."

He'll take to the court in the first week of January at the Hopman Cup, a team event in Perth.

Later, if Federer does end his four-year title drought at majors, he would become the second oldest man to win a grand slam in the Open Era, behind Ken Rosewall.

Wimbledon remains the most likely venue, given it has been Federer's most successful major with seven titles.

Sharapova's reception

Sharapova is scheduled to return at the end of April, at which time the five-time grand slam winner -- and for most of the last decade the richest female athlete in the world -- would have served her 15-month suspension for testing positive for meldonium.

Could Sharapova win a grand slam? Don't count her out, especially if Williams isn't in her way. Sharapova's motivation is bound to be soaring.

What will Kyrgios do next?

It's extremely rare for the ATP to sanction one of its own players but the men's tour has done it two seasons in a row to Nick Kyrgios. Hence the "bad boy" tag.

After Kyrgios directed a lewd on-court sledge at Stan Wawrinka and his girlfriend in 2015, the ATP fined him $10,000 and handed him a suspended ban; then this October he was suspended for eight weeks -- through the middle of January -- and fined more than $40,000 for not trying in a match at the Shanghai Masters.

Kyrgios, like Federer, will make his return at the Hopman Cup, which isn't an ATP event and thus not related to the suspension.

Kyrgios-- you want to be the best-- come see me-- you will learn to play, excite, and to win!! It's you choice-- or just be mediocre!gd luck

Currently without a coach, the likes of eight-time grand slam champion Jimmy Connors and Kyrgios' fellow Aussie, former Wimbledon finalist Mark Philippoussis, have offered to work with the 21-year-old, but just how much motivation Kyrgios has to make changes remains to be seen.

He told the New York Times in August that he planned to retire by 27 and has often claimed he likes basketball much more than tennis.

Serena's quest for No. 23

Williams' charismatic coach, Patrick Mouratoglou, set the bar high for his charge when discussing future grand slam titles. He is targeting 30, eight more than her current haul.

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Given her age -- 35 like Federer -- that may be optimistic, but odds are that the American will edge ahead of Graf, who also holds 22 majors to share the Open Era record: Williams has won a major in each of the past five seasons.

Also like Federer, she has been slowed by injuries. Though Williams -- especially in recent times -- has never been one to overload her schedule, she was limited to eight tournaments in 2016 and, hindered by shoulder troubles, shut down her season post the US Open for the second year running.

Williams didn't compete in the IPTL as originally planned because of the aforementioned financial constraints of the league; she will return the first week of January and make her first appearance at Auckland's ASB Classic.